Unwinder

ABSTRACT

The present invention relates to an unwinder for a packaging machine, in particular for a thermoformer or tray sealer, comprising a holding mandrel provided for receiving thereon a film reel having a film wound thereon. The unwinder comprises a measuring module configured to detect a distance to an end face of the film wound on the film reel and/or a distance to a stop member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application claims priority to German Application Number 102012001816.9 filed Jan. 31, 2012, to Luciano Capriotti and Andreas Gschwind entitled “Unwinder,” currently pending, the entire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an unwinder that may be primarily used in the field of packaging machines.

BACKGROUND OF THE INVENTION

An unwinder for a tray sealer is already known to those skilled in the art. The unwinder comprises a film unwinder as well as a film winder. The film unwinder comprises a holding mandrel provided for carrying a film reel. The holding mandrel is secured to a housing supported on the tray sealer. The film is fed from the film unwinder into the packaging machine for a sealing process. A residual film resulting from the sealing process is wound by means of the film winder.

It is important that the film reel is positioned on the holding mandrel such that tensions in the film material are prevented. If this is not the case, wrinkles may be formed in the film material. In addition, sealing and cutting errors may occur during the packaging process due to malpositioning of the film reel on the holding mandrel, and this would be problematic especially in the case of imprinted films

In practice, color marks are often applied to the holding mandrel for the purpose of orientation. Such color marks do, however, not lead to precise positioning of the film reel on the holding mandrel. Moreover, such color marks are often smeared when the film reel is pushed onto the holding mandrel. Hence, fixing the film reel in position on the holding mandrel often corresponds to approximate rather than precise positioning.

It happens quite frequently that the film material is not centrally wound on the film reel. If the operator orients himself only according to the film reel carrying the film material, undesired tensions may be caused in the film material during the packaging process. It is also a well-known fact that film manufacturers use different film reels for the same film format, the film material being wound onto these film reels. It is therefore important that primarily the film material, and not the film material-carrying film reel itself, is correctly positioned on the holding mandrel so as to prevent undesired tensions in the film material.

In view of the above-shown technical difficulties and drawbacks occurring in practice, it is the object of the present invention to improve an unwinder for a packaging machine such that, by means of simple, structural technical features, it will favor fast film exchange and prevent tearing of the film as well as cutting and sealing errors during the packaging process.

SUMMARY OF THE INVENTION

The unwinder according to the present invention is suitable for use with a packaging machine, in particular a thermoformer or a tray sealer, and comprises a holding mandrel provided for receiving thereon a film reel having a film wound thereon.

The present invention is so conceived that the unwinder may comprise a measuring module configured to detect a distance to an end face of the film wound on the film reel.

According to the present invention, the film reel as such is provided as a carrier for the film. The film is wound onto the film reel in a substantially cylindrical fashion. The wound film comprises two approximately circular end faces, one of said end faces being directed towards the measuring module, when the film reel with the film is positioned on the holding mandrel of the unwinder. The dimensions of the respective end face are defined by the sum of the superimposed edges of the film. In addition, the wound film defines a cylindrical circumferential surface. The circumferential surface defines, together with the two end faces, the surface of the wound film.

The present invention offers the technical advantage that positioning of the film material relative to the holding mandrel can be carried out independently of the film reel carrying the film material.

In addition, the invention offers the possibility of rapidly replacing an empty film reel by a new one.

Furthermore, the operator can rely on the precision of the measuring module and does not have to apply himself any marks by hand.

Finally, the reject rate can be kept low by the unwinder according to the present invention, since, making use of the invention, a reduced amount of sealing and cutting errors will occur. Furthermore, the unwinder is able to supply the film material to the packaging machine such that uniform sealing will be accomplished. This is highly advantageous, especially when the film material used has already been printed on, since the imprint can thus be applied to the package uniformly and at a precise position.

Likewise, the unwinder according to the present invention is capable of preventing a formation of wrinkles during the packaging process, which would lead to machine downtimes and, consequently, increase the manufacturing costs.

In addition to or alternatively to a measurement of a distance between the measuring module and the end face of a film, the measuring module may also be configured to measure a distance to a stop member supported on the holding mandrel such that it is displaceable thereon in the axial direction of the holding mandrel. Irrespectively of whether or not a film reel is provided, it would thus be possible to axially adjust, e.g. displace, the stop member on the holding mandrel until it can be guaranteed that a film reel that will be moved into contact with the stop member later on will occupy precisely the desired position on the holding mandrel.

In one embodiment, the measuring module is mounted on a housing or, at least sectionwise, in a housing of the unwinder. The housing offers a stable base for fixing the measuring module. The measuring module may be, at least partly, arranged in the housing of the unwinder. Easy cleaning of the unwinder including the measuring module can be achieved in this way. In addition, the housing offers sufficient protection to the unwinder of the measuring unit.

According to a further embodiment of the invention, the measuring module is mounted between the housing and the film reel held by the holding mandrel. The end face of the film can thus be easily measured by the measuring module.

It will also be of advantage when a measurement path established by the measuring module extends parallel to an axis of the holding mandrel. The measurement path of the measuring module may, for example, be parallel to an axis of rotation of the holding mandrel, if the latter is supported such that it is rotatable relative to the housing. Alternatively, the measurement path may, however, also extend at an angle relative to the axis of the holding mandrel. This allows a particularly flexible arrangement of the measuring module on the unwinder.

According to a further embodiment of the present invention, the holding mandrel is supported such that it is rotatable relative to the housing. This allows particularly easy unwinding of the film from the film reel.

The holding mandrel can include a tensioning device provided for securing the film reel in position on the holding mandrel. The tensioning device offers the technical advantage that the film reel can be secured in position on the holding mandrel so as not to slip.

A further improvement of the present invention is so conceived that the measuring module comprises at least one contactless sensor. This sensor offers a particularly good mode of operation and is excellently suitable for use with packaging machines in the food sector. In addition, a contactless sensor can be obtained at a reasonable price and it offers a longer service life. The sensor may be a distance sensor. A distance between the measuring module and the end face of the film can be detected precisely by means of the distance sensor. Alternatively, a proximity switch can be provided instead of the distance sensor. The proximity switch is configured such that it will output a switch signal primarily when the film approaches the measuring module.

The contactless sensor may also be a light, IR radiation, radio wave, microwave, terahertz radiation or ultrasonic sensor. A distance measurement between the measuring module and the end face of the film can be executed by means of transit time and phase position measurement carried out with radio waves, light, infrared or ultrasound. In addition, the invention may be so conceived that the distance measurement can be carried out by means of triangulation.

It is also imaginable to use an inductive or capacitive sensor as the contactless sensor. This kind of sensor will primarily be of advantage when the film contains metallic components.

A further embodiment is so conceived that the holding mandrel is connected to the unwinder through a releasable flange unit. The holding mandrel can be replaced by some other holding mandrel having a different size in this way. This is important, since film manufacturers use different film reel formats.

When a stop member is provided, it will be expedient to configure it such that it is adapted to be locked in position on the holding mandrel as soon as it has reached an arbitrary axial target position. It is also a question of expediency to provide locking of such a nature that it can be released later on, so that the stop member can be displaced for receiving a differently dimensioned film. The stop member may, for example, be provided with a clamping mechanism for the purpose of releasable locking. A particularly advantageous embodiment is a stop member that is steplessly adjustable on the holding mandrel in the axial direction.

A drive unit may be provided, which controls a movement of the holding mandrel. Unwinding of the film from the film reel is facilitated in this way.

A special embodiment is so conceived that the measuring module is functionally connected to an operating panel of the packaging machine. The operating panel is suitable for use as an excellent interface between the packaging machine and the operating staff. It offers to the operating staff a simple tool for controlling and operating the unwinder as well as the packaging machine.

Operating elements can be provided, by means of which an exchange of the film reel can be controlled, the operating elements being configured for controlling release of the film reel from the holding mandrel or mounting of the film reel on the holding mandrel. The operating elements may, by way of example, be implemented as mechanical switches or as touch-sensitive keys. In particular, the operating elements may be provided on the operating panel so that the operating staff will be able to control an exchange of films centrally at the operating panel.

According to another embodiment of the present invention, the packaging machine and/or the unwinder comprises a control unit by means of which the distance measured by the measuring module can be detected as a measurement signal. By means of the control unit, the measurement signal can be further processed such that it will be available for other functions of the unwinder and the packaging machine, respectively.

It will also be of advantage when a memory is provided, in which the distance to the film, measured by the measuring module, can be stored. The measurement value stored in the memory is retrievably stored and can be compared with a re-measured measurement value.

A switch can be provided, which, when actuated, allows to store in the memory a nominal distance between the end face of the film and the measuring module, especially when a film reel having specific dimensions is secured in position for the first time. By actuating the switch once more, the nominal distance stored in the memory can be replaced by a new nominal distance, e.g. when a new film format is placed in position. By means of such a teach function, the changeover times of subsequent exchange operations of films having the same format can be reduced.

The packaging machine can be configured for defining an admissible tolerance field around the nominal distance. The operating staff can thus execute an exchange of films more easily.

According to a further embodiment of the invention, the packaging machine is configured for checking whether the measured distance to the end face of the film corresponds to a value of the defined tolerance field. This can especially be done by the control unit connected to the measuring module. An excellent control function is thus offered for identifying whether the film reel and especially the film material wound thereon occupy the desired position on the holding mandrel.

An embodiment can be so conceived that fixing the film reel in position on the holding mandrel can be executed, when the measured distance between the measuring module and the end face of the film lies within the tolerance field. Incorrect fixing of the film reel on the holding mandrel can be prevented in this way.

A further embodiment of the present invention may be so conceived that a packaging process can only be started, when fixing of the film reel to the holding mandrel has been executed within the defined tolerance field. The packaging machine will thus only start when the risk of reject production has been reduced.

According to another embodiment of the invention, a signaling unit is provided, which is configured for outputting acoustically and/or visually a predetermined signal to an operator, and which can thus indicate whether the film is correctly positioned on the holding mandrel. This will additionally support the operating staff in securing the film reel in position on the holding mandrel.

Acoustic signaling may here, for example, consist of a sustained tone that is reached when the measured distance to the end face of the film lies within the tolerance field. By detecting a distance outside the tolerance field, a recurring tone can preferably be output. It would also be possible to emit the recurring tone at intervals of decreasing lengths, when the measured distance to the end face of the film approaches a tolerance limit of the tolerance field and/or to produce the recurring tone at intervals of increasing lengths, when the measured distance drifts increasingly away from the tolerance field. This will lead the operator to optimum positioning of the film on the holding mandrel.

Visual signaling, however, may be realized on a display of the operating panel. According to one embodiment, a traffic light representation may, for example, be used for displaying the measured distance to the film relative to the tolerance field. A large distance between the film and the tolerance field may here be indicated by a red light, whereas a measured distance lying within the tolerance field may be represented in the form of a green. light.

Visual signaling, however, may be realized on a display of the operating panel. According to one embodiment, a traffic light representation may, for example, be used for displaying the measured distance to the film relative to the tolerance field. A large distance between the film and the tolerance field may here be indicated by a red light, whereas a measured distance lying within the tolerance field may be represented in the form of a green light.

Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.

DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

In the accompanying drawing, which forms a part of the specification and is to be read in conjunction therewith in which like reference numerals are used to indicate like or similar parts in the various views:

FIG. 1 shows a packaging machine with an unwinder according to one embodiment of the present invention,

FIG. 2 shows a first embodiment of the unwinder according to the present invention, and

FIG. 3 shows a second embodiment of the unwinder according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. For purposes of clarity in illustrating the characteristics of the present invention, proportional relationships of the elements have not necessarily been maintained in the drawing figures.

The following detailed description of the invention references specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The present invention is defined by the appended claims and the description is, therefore, not to be taken in a limiting sense and shall not limit the scope of equivalents to which such claims are entitled.

FIG. 1 shows a packaging machine 10, here a tray sealer 10, having an unwinder 1 according to one embodiment of the present invention mounted thereto. The unwinder 1 comprises a film feed unit 2 and a residual film winder 3. When seen in the direction of transport F, the film feed unit 2 is mounted to the packaging machine 10 at the inlet thereof. The residual film winder 3 is mounted to the packaging machine 10 at the outlet thereof. During the packaging process, a film 4 is advanced from the film feed unit 2 to the residual film winder 3 through the packaging machine 10 so as to provide the film for a sealing process in the latter.

The film feed unit 2 according to FIG. 1 includes a holding mandrel 5. The holding mandrel 5 is supported on a housing 6 of the film feed unit 2. In addition, the film feed unit 2 includes a measuring module 7 arranged within the housing 6 according to FIG. 1.

FIG. 1 also shows that an operating panel 8 is mounted on the packaging machine 10. The operating panel 8 can be movably arranged on the packaging machine 10 by means of a holder 9. The operating panel 8 may be functionally connected to the measuring module 7 of the unwinder. This is schematically shown by the broken line 11. The operating panel 8 comprises a display 12. The display 12 is used for visually representing operating functions of the packaging machine 10 and of the unwinder 1. In addition, the operating panel 8 can comprise a control unit 13 configured for processing a measurement signal of the measuring module 7.

In a lower area of the operating panel 8, a speaker 14 may be additionally provided, said speaker being configured for outputting acoustic signals.

Above the control unit 13, a memory 15 is shown. The memory 15 is functionally connected to the control unit 13, said memory 15 being adapted to store therein a measurement value received from the control unit 13.

The operating panel has also provided thereon a switch 16, which, when actuated, allows a distance measured by the measuring module 7 to be stored in the memory 15 as a measurement value.

FIG. 2 shows an enlarged representation of the film feed unit 2 of the unwinder 1 in accordance with one embodiment of the present invention. The measuring module 7 is mounted on a surface of the housing 6, and it detects a distance to an end face 23 of the film 4. The end face 23 is defined by the sum of the superimposed edges of the film 4. Together with a circumferential surface 35, the two end faces 23 define a surface of the wound film 4. The film 4 is wound on a film reel 17 provided as carrier of the film 4. The film reel 17 having the film 4 wound thereon is secured in position on the holding mandrel 5 of the unwinder 1.

FIG. 2 also shows a stop member 18 comprising a clamping mechanism, which is not shown. At the release position, the stop member 18 is steplessly movable on the holding mandrel 5 in the axial direction of the latter, whereas, at the locking position, the stop member 18 occupies a fixed axial position on the holding mandrel 5. At this locked position of the stop member 18, a film reel 17 can be displaced on the holding mandrel 5 until it comes into contact with the stop member 18 so as to occupy a defined axial position on the holding mandrel 5.

According to FIG. 2, the measuring module 7 is arranged on a surface 19 of the housing 6, but, as shown by a broken line, a certain portion thereof may also project into the housing 6. The housing 6 has additionally provided thereon a mount 20 used for mounting the film feed unit 2 to the packaging machine 10.

A first measurement path 21 extends from the measuring module 7 to the end face 23 of the film 4 and a second measurement path 22 extends from the end face 23 back to the measuring module 7.

In addition to or alternatively to the configuration shown in FIG. 2, a configuration is imaginable in which the measuring module 7 is positioned closer to the axis of the holding mandrel 5 and adapted to detect the axial distance between itself and the stop member side facing the housing 6. This would allow determination of the axial position of the stop member 18 on the holding mandrel 5 so that a film reel 17 pushed into contact with the stop member 18 would occupy a defined axial position on the holding mandrel 5.

FIG. 3 shows an unwinder 1 according to another embodiment of the present invention, which is functionally connected to the operating panel 8 of the packaging machine 10. In particular, the measuring module 7 of the unwinder 1 is functionally connected to the control unit 13 of the operating panel 8. This functional connection is schematically shown by the broken line 11.

In FIG. 3, the control unit 13 is configured as a component part of the operating panel 8. The measuring module 7 may be arranged within the housing 6 of the unwinder 1 according to FIG. 3. The measuring module 7 may comprise a sensor 24 implemented as a distance or proximity sensor and configured for detecting a distance to the end face 23 of the film 4 in a contactless manner. The sensor 24 can be arranged in the measuring module 7 such that it is substantially flush with a surface of the housing 6.

The distance between the measuring module 7, in particular between the sensor 24, and the end face 23 of the film 4 is defined by the first measurement path 21 and the second measurement path 22. As can be seen from FIG. 3, the first measurement path 21 and the second measurement path 22 extend parallel to a support axis 25 of the holding mandrel 5. A parallel orientation of the first and second measurement paths 21, 22 relative to the support axis 25 is, however, not absolutely necessary.

In addition to the measuring module 7, also a drive unit 26 can be provided in the housing 6 of the unwinder 1. The drive unit 26 is connected to the holding mandrel 5 of the unwinder 1 in such a way that it is capable of rotating the holding mandrel 5 about the support axis 25 so as to unwind the film 4. Alternatively to the drive unit 26, the structural design may be such that the holding mandrel 5 is only rotatably supported on the unwinder 1, in particular on the housing 6 of the unwinder 1, without the drive unit 26 being additionally provided.

FIG. 3 also shows that the holding mandrel 5 includes a tensioning device 27. The tensioning device 27 secures the film reel 17 on the holding mandrel 5 and is capable of preventing a lateral displacement of the film reel 17 on the holding mandrel 5 during unwinding of the film 4.

In addition, FIG. 3 shows a tolerance field 28 having lower and upper tolerance field limits 29, 30 relative to the end face 23 and relative to the measured distance between the measuring module 7 and the end face 23. The operating panel 8 is configured for determining the lower and upper limits 29, 30 of the tolerance field 28 on the basis of a nominal distance 31 stored in the memory 15. Furthermore, the operating panel 8 can be configured for detecting whether the measured distance between the measuring module 7 and the end face 23 of the film 4 lies within the tolerance field 28, i.e. between the lower and upper limits 29, 30, and corresponds thus to the nominal distance 31.

The display 12 may have provided thereon touch-sensitive operating elements 32. The touch-sensitive operating elements 32 may be provided at various points of the display 12 and they are configured for controlling an exchange of the film reel 17. To this end, the operating elements 32 are functionally connected to the tensioning device 27. For releasing the film reel 17 from the holding mandrel 5, the tensioning device 27 can be controlled by the operating elements 32 such that it will release the film reel 17 from the holding mandrel 5. It is, however, also possible that the tensioning device 27 is controlled by the operating elements 32 such that it will tension the film reel 17 onto the holding mandrel 5.

FIG. 3 also shows that the operating panel 8 includes a signaling unit 33. The signaling unit 33 is configured for outputting a visual and/or an acoustic signal. In the case of a visual signal, the signaling unit 33 can output the signal via an area of the display 12. Alternatively or in addition thereto, the signaling unit 33 can output an acoustic signal via the speaker 14.

Finally, FIG. 3 shows the switch 16 which, when actuated, allows to store the nominal distance 31 between the end face 23 of the film 4 and the measuring module 7 in the memory 15 of the operating panel 8, especially when a film reel 17 having specific dimensions is secured in position for the first time.

In the following, it will now be described how the unwinder 1 according to the present invention can primarily be used in practice.

If the film reel 17 and the film 4 wound thereon is secured in position on the holding mandrel 5 of the unwinder 1 for the first time, the nominal distance 31 will be stored in the memory 15 of the operating panel 8. To this end, the film reel 17 is positioned on the holding mandrel 5 such that the distance between the measuring module 7 and the end face 23 of the film 4 corresponds to the nominal distance 31. As soon as the film reel 17 has reached the desired position on the holding mandrel 5, the operator operates the switch 16 so as to store the desired nominal distance 31 in the memory 15. As soon as the nominal distance 31 has been safely stored in the memory 15, the unwinder 1 allows the film reel 17 to be secured in position on the holding mandrel 5 by means of the tensioning device 27. The fastening of the film reel 17 on the holding mandrel 5 can finally be controlled by an operating element 32 of the operating panel 8.

The invention can be so conceived that, during unwinding of the film 4 from the film reel 17, the measuring module 7 is adapted to be switched to an idle mode, for example, by the operating panel 8, since detecting the distance to the end face 23 of the film 4 during unwinding would lead to an unnecessary consumption of power and since it can also be assumed that the film reel 17 will not shift along the holding mandrel 5. As soon as the film 4 has been consumed completely, the operator can release the film reel 17 from the holding mandrel by unlocking the tensioning device 27 by means of the operating panel 8. Once the tensioning device 27 has been unlocked, the operator can remove the empty film reel 17 from the holding mandrel 5 and place onto the holding mandrel 5 a new film reel 17 having the film 4 wound thereon.

For positioning a new film reel 17 having the film 4 wound thereon, the operator can reactivate the measuring module 7 so that it will detect the distance to the newly positioned film 4 and compare this distance with the previously ascertained nominal distance 31, which has been stored in the memory 15. In addition, the invention can be so conceived that the control unit 13 is configured for checking whether the measured distance lies within the tolerance field 28. The tolerance field can be generated automatically by the control unit 13 as soon as the nominal distance 31 has been stored in the memory 15.

The present invention is also so conceived that, as along as the new film reel 17 has not reached a desired position on the holding mandrel 5, it will cause generation of a signal. As long as the operator moves the end face 23 at a distance from the measuring module 7 which does not lie within the tolerance field 28, a visual and/or acoustic signal is imparted to the operator in order to assist him. The acoustic signal can be outputted from the speaker 14 of the operating panel 8. Alternatively or additionally thereto, a visual signal may be displayed on the display 12, for example, through the traffic light representation 34.

In order to indicate to the operator a desired positioning of the film 4 relative to the measuring module 7, the acoustic signal may, for example, approach a continuous beep and become such a continuous beep, when the detected distance corresponds to the nominal distance 31 or lies within the tolerance field 28.

The traffic light representation 34 may be configured for indicating to the operator a correct positioning of the film 4 relative to the measuring module 7 with due regard to the nominal distance 31 and the tolerance field 28, respectively, when the traffic light representation 34 is switched to green. A red signal light of the traffic light representation 34 will, however, indicate to the operator that the film 4 is still too far away from a desired position on the holding mandrel 5, whereas an orange-colored signal output of the traffic light representation 34 stands for an approach to the desired position of the film 4 relative to the measuring module 7.

The unwinder 1 according to the present invention can be used in practice for precise positioning of a film reel having a film wound thereon. Such precise positioning of the film 4 on the unwinder according to the present invention allows to prevent the creation of tensions in the film material. In this way, the film can be prevented from wrinkling; such wrinkling would lead to long changeover times and rejects. The unwinder 1 according to the present invention can be used in a particularly advantageous manner for the purpose of a changeover of films. In this case, it will support the operator in rapidly establishing a new film so that the production process can be continued without majors interruptions. Other characteristic features of the unwinder according to the present invention are an ergonomic and user-friendly application.

From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure. It will be understood that certain features and sub combinations are of utility and may be employed without reference to other features and sub combinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments of the invention may be made without departing from the scope thereof, it is also to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted as illustrative and not limiting.

The constructions and methods described above and illustrated in the drawings are presented by way of example only and are not intended to limit the concepts and principles of the present invention. Thus, there has been shown and described several embodiments of a novel invention. As is evident from the foregoing description, certain aspects of the present invention are not limited by the particular details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. The terms “having” and “including” and similar terms as used in the foregoing specification are used in the sense of “optional” or “may include” and not as “required”. Many changes, modifications, variations and other uses and applications of the present construction will, however, become apparent to those skilled in the art after considering the specification and the accompanying drawings. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow. 

What is claimed is:
 1. An unwinder for a packaging machine, in particular for a thermoformer or tray sealer, said unwinder comprising: a holding mandrel configured for receiving thereon a film reel having a film wound thereon; and a measuring module configured to detect a distance to an end face of the film wound on the film reel and/or a distance to a stop member supported on the holding mandrel such that it is displaceable thereon in the axial direction of the holding mandrel.
 2. The unwinder of claim 1 further comprising a housing and wherein the measuring module is mounted on or in the housing.
 3. The unwinder of claim 2 wherein the measuring module is mounted between the housing and the film reel held by the holding mandrel.
 4. The unwinder of claim 1, wherein a measurement path established by the measuring module extends parallel to an axis of the holding mandrel.
 5. The unwinder of claim 1, wherein the holding mandrel includes a tensioning device provided for securing the film reel in position on the holding mandrel.
 6. The unwinder of claim 1, wherein the measuring module comprises at least one contactless sensor.
 7. The unwinder of claim 1, wherein the stop member is adapted to be locked in position on the holding mandrel.
 8. The unwinder of claim 1, wherein the measuring module is functionally connected to an operating panel of the packaging machine.
 9. A packaging machine comprising: an unwinder including: a holding mandrel configured for receiving thereon a film reel having a film wound thereon; and a measuring module configured to detect a distance to an end face of the film wound on the film reel and/or a distance to a stop member supported on the holding mandrel such that it is displaceable thereon in the axial direction of the holding mandrel.
 10. The packaging machine of claim 9 further comprising operating elements by means of which an exchange of the film reel can be controlled, the operating elements being configured for controlling release of the film reel from the holding mandrel or mounting of the film reel on the holding mandrel.
 11. The packaging machine of claim 9 further comprising a control unit by means of which the distance measured by the measuring module can be detected as a measurement signal.
 12. The packaging machine of claim 9 further comprising a memory in which the distance to the film, measured by the measuring module, can be stored.
 13. The packaging machine of claim 12 further comprising a switch, which, when actuated, allows to store in the memory a nominal distance between the film or the stop member and the measuring module, especially when a film reel having specific dimensions is secured in position for the first time.
 14. The packaging machine of claim 13, wherein the packaging machine is configured for defining an admissible tolerance field around a nominal distance.
 15. The packaging machine of claim 14, wherein the packaging machine is configured for checking whether the measured distance to the film corresponds to a value of the defined tolerance field.
 16. The packaging machine of claim 14, wherein fixing the film reel in position on the holding mandrel can be executed, when the measured distance between the measuring module and the film or the stop member lies within the tolerance field.
 17. The packaging machine of claim 9 further comprising a signaling unit, which is configured for outputting acoustically and/or visually a predetermined signal to an operator, and which is configured for indicating whether the film is correctly positioned on the holding mandrel. 